LiroxtronIV (LiroxtronIV)-
explain what is meant by reversible reaction
reaction which can proceed in both → & ← directions; equilibrium reached when both pdt, rxt present in reaction mixture
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explain what is meant by dynamic equilibrium
refers to state of balance in reversible rxn >
rate of → rxn = rate of ← rxn >
conc of all rxt, pdt remain constant
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state La Chatelier's Principle
when system @ equilibrium disturbed by △ in conditions, POE shifts to counteract effect of change, re-establish equilibrium
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describe effects of changes in conc/partial pressure on system at equilibrium and its equilibrium constant
system
species added/removed, conc/partial pressure ↑/↓ >
by LCP, system favours →/← rxn to remove/form species in order to decrease/increase [species], re-establish equilibrium >
>pdt react to produce >rxt/>rxt react to produce >pdt
Kc/Kp
not affected
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describe effects of changes in total pressure on system at equilibrium and its equilibrium constant
system
pressure inversely proportional to volume
volume ↑/↓, total pressure ↓/↑ >
by LCP, system favours →/← rxn to increase/decrease total no. of gas particles to ↑/↓ total pressure >
POE shifts → ←
Kc/Kp
not affected
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describe effects of changes in temp on system at equilibrium and its equilibrium constant
system
△H>0, endothermic
△H<0, exothermic
temp ↑/↓, system favours →/← rxn to absorb/evolve some heat to ↓/↑ temp
Kc/Kp
when →/← rxn favoured, [pdt]/[rxt] △!!!
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define equilibrium constant(Kc) in terms of conc
aA + bB ⇌ cC + dD
Kc = [C]ceqm[D]deqm/[A]aeqm[B]beqm
unit of Kc = (moldm-3)(c+d)-(a+b)
[H2O(l)] omitted when...
eqm in aq medium, H2O is solvent, [H2O] >>
[H2O(l)] relatively constant, amount formed/reacted away very small
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define equilibrium constant(Kp) in terms of partial pressures
(gaseous systems only)
aA(g) + bB(g) ⇌ cC(g) + dD(g)
Kp = pCc x pCd /pCa x pCb
pX = partial pressure of gas X @ eqm(atm,Pa,Nm-2)
unit of Kp = (atm/Pa/Nm-2)(c+d)-(a+b)
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how is position of equilibrium(K) dependent on ∆GƟ?
∆GƟ > 0(spontaneous), K > 1, then;
position of eqm lies far right(K>>1, reaction proceeds near completion)
∆GƟ < 0(non-spontaneous), K < 1, then;
position of eqm lies far left(KK<<1, reaction hardly proceeds)
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describe and explain conditions of Haber process
N2(g) + 3H2(g) ⇌ 2 NH3(g), ∆HƟ=−92kJmol−1
optimum temp
450-500oC
low temp shifts POE →, favour → rxn >
NH3(g) yield ↑, but rate too slow @ low temp >
moderate temp(450-500oC) allow reach POE @ higher rate while relatively high yield
optimum pressure
200-250atm
high pressure shifts POE →, favour → rxn >
NH3(g) yield ↑, reach POE ↑, but too ex >
moderate pressure(200-250atm) allow relatively high yield @ low cost
catalyst
finely divided Fe catalyst
reach POE @ faster rate; catalyst ↑ rate of both →/← rxn by same extent >
yield constant
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how to calculate Kc/Kp or equilibrium quantities of species from data?
use ICE; Initial, Change, Equilibrium
quantities in mol, moldm-3, atm >
calculate eqm amount of species in rxn >
form Kc/Kp eqn with units >
obtain Kc/Kp or eqm quantity of species
